Launder washers



1959 D. R. MITCHELL ET AL 2,912,109

LAUNDER WASHERS Filed Jan. 10, 1957 D QM. n J O Q Q Q MN m ON a m 9 0 mm INVENTORS David R. Mitchell James O'Brien *W Lira/f United States Patent LAUNDER WASHERS David R. Mitchell, State College, and James OBrien,

Nemacolin, Pa., assignors to The Buckeye Coal Company, Youngstown, Ohio, a corporation of Pennsylvania Application January 16, 1957, Serial No. 633,483

13 Claims. (Cl. 209-458) This invention relates to launder washers for the concentration and classification of ores and minerals according to their specific gravity.

The use and construction of launder washers is old and well known in the art. They have been used for many years for the concentration of ores and minerals and can be operated to classify the treated products at a desired specific gravity. Perhaps the best known launder washers are those known as Rheolaveur launders. 'Ihey find particular use in the preparation of coal for the separation of pure coal from impurities and from coal with inclusions of impurities. In the conventional operation of Rheolaveur launders the coal to be cleaned is fed into an inclined launder chute or trough in which it is subjected to the action of a stream of Water, generally known as push water. The push water carries the coal particles along the trough with suflicient fluidity for the coal to become stratified with particles of higher density becoming segregated along the bottom of the trough. The initial section of the trough frequently has a steeper slope than the subsequent section and serves to impart high velocity and fluidity to the incoming particles.- As the slope decreases, the particles become segregated according to their specific gravity and form a bed in the trough. A number of particle outlets or boxes are provided beyond the initial slope for the withdrawal of heavier particles. A barrier or barrage is customarily placed across the width of the trough downstream from each box. The bed of particles builds up behind each barrage and permits Stratification within the bed. Barrages may also be installed at other points along the trough to aid in forming a bed. Water is customarily fed into some of the boxes, and means are provided to adjust the flow. Water flows out through an orifice or opening in the bottom of the box carrying with it those particles which have been withdrawn from the trough, and water may also flow upwardly from the box to the or a change in the rate or the character of the feed will all cause malfunctioning of the launder. The orifices at the bottom of the boxes wear to a larger size from the passage of material and permit more Water to escape through the bottom. The barrages likewise become worn in time. Thus, it is necessary to make constant replacements of the orifices and barrages to maintain constant operating conditions.

Even when Rheolaveur launders are well operated, it has not heretofore been possible to make a completely accurate separation. It has been a frequent practice to subject at least some of the Rheolaveur product to further treatment and separation on concentrating tables.

. We provide r'neans'in the trough of a launder washer to divide a bed of moving particles adjacent to at least one of the boxes of the launder. We prefer to provide a plurality of thin flat means above some of the boxes extending between the side Walls of the launder trough. Preferably, said means are vertically adjustable and are provided with adjusting means. In our preferred embodiment we employ a plurality of thin flat plates adjustably positioned parallel to the bottom of the trough each forming a thin fiat passage to the associated outlet and preventing material above the passage from being drawn directly down into the outlet. We prefer to provide a launder trough having a smooth unobstructed surface for the flow of particles therethrough.

Other details, objects and advantages of our invention will become apparent as the following detailed description of a present preferred embodiment thereof proceeds.

' In the accompanying drawings we have illustrated a present preferred embodiment of our invention in which Figure l is a side elevational View of a five unit free discharge launder system embodying our invention;

' Figure 2 is a side elevational view in cross-section of one of the boxes of the launder in Figure l but shown in greater detail; and

trough. The flow of water to the box is usually adjusted to provide a slightly rising velocity from the box into the trough, preventing lighter density particles from settling into the box.

Those particles which go over every box to the end of.

the trough are of light specific gravity and in the case of coal constitute highest grade product obtained from the feed. The particles withdrawn in the first boxes are those of heavier gravity and constitute refuse or gangue. Particles withdrawn in later boxes normally constitute a mixed product termed middlings and are usually recirculatedthrough the washer.

It is common practice to provide a number of troughs, one above another, which work together as a unit, particularly in the case of free discharge launders for washing fine coal. Boxes are provided on the several troughs and push water may be added in the different troughs. The operation of launders has always been diflicult and has required continuous attention to insure that a proper separation is made. Too much or too little push Water, an improper rising velocity of water in the boxes,

Figure 3 is a top view of the box shown in Figure 2.

The launder system is composed of five flights or levels which are conventionally designated A, B, C, D, and E launders from top to bottom. A and B launders are comprised of two parallel lanes side by side, while C, D, and E launders are single lane. Raw coal 1 and push Water 2 are fed into the upper end of A launder by distributing means which are well known in the art. Recirculated middlings may also be fed to A launder with the raw coal and push water. A plurality of boxes are positioned along the lower side of A, B, C, D, and E launders and discharge into the chutes below. Boxes 3 discharge into chute 4 going directly to C launder. Box

A was installed in the launder for conventional operation but has not been used since the installation of our invention in the launder. The remaining boxes in A launder discharge into B launder, and all of the boxes in B launder discharge into C launder. In view of the reduction. in width between B launder and C launder, wings 5 are provided to-direct the discharge from the boxes of B launder into C launder. During conventional operation boxes '6 of C launder discharge into chute 7 which discharges to refuse. They have been closed off similarly to box 4. Boxes 9 in D and E launders have associated with them dividing plates and are illustrated in greater detail in Figures 2 and 3. Box 9 is a double box, but is similarly equipped. The remaining boxes 10 in E launder were originally installed but are no longer needed and have been closed off. Thus, all of the boxes discharging into refuse chute 7 embody our invention. The A launder overflow 11 and B launder overflow 12 are dewatered and then placed upon the clean coal conveyor to be loaded out of the plant. C launder overflow 13 may be placed upon the clean coal conveyor or it may be recirculated as a middling product to the head end of A launder. Alternatively, it may be skimmed with the lower part of the overflow being recirculated and the upper part leaving the plant as clean coal. D launder overflow 14 and E launder overflow 15 are recirculated as middlings and are returned to A launder with the raw coal and push water. Refuse discharging from the boxes into chute 7 leaves the chute at 31.

Referring to Figures 2 and 3, the bottom wall 16 of the launder trough and side walls 17 form a generally rectangularly shaped trough. An outlet 18 provides access to box 19 and extends across the entire width of the trough between side walls 17. A pipe 20 leads to the interior of box 19, supplying water to the box behind wall 21. Wall 21 serves to even out the incoming water flow to provide a rising velocity through vertical passage 22 which is uniform from side to side. Such boxes are conventional and may have one outlet as shown in the drawings or may have two outlets. In double boxes an inverted U-shaped baflle is provided between the two outlets. In the conventional launder installations, a barrage is placed across the launder trough a short distance downstream from each box to form a bed of material in the trough above and upstream from the box. A movable plate member 23 has an orifice 24 which controls the discharge of material from the box. Plate member 23 may be rotated to place a solid portion of the plate member in a solid position below the lower box opening, thereby blocking off discharge from the box.

A dividing plate is positioned in the trough above outlet 18. An angle 2.5 is placed across the trough and has welded thereon a bushing 26 in which a threaded shaft 27 is slidably mounted. Handwheel 28, which is threaded on shaft 27 above bushing 26, may be rotated to cause vertical movement of shaft 27. A thin flat plate 29 is welded to thelower end of shaft 27. It extends between side walls 17 thus preventing unrestricted vertical access to outlet 18. The leading edge 30 is positioned in advance of outlet 18. The plate forms a restricted passage along the bottom wall 16 of the launder trough from which passage outlet 18 opens. Preferably, the plate and shaft 27 present as little obstruction as possible to the moving bed in the trough. No barrages are installed in the launder troughs, and there is no restriction either upstream or downstream from the outlet.

In the operation of launders embodying the instant invention, the coal to be separated is fed to the launder in the usual way. The absence of any barrages in the launder trough results in a particle bed which is extremely fluid and freely moving. For a given feed the depth It will be understood, however, that some heavy density particles will be carried in the upper strata and that some light density particles will be carried in the lower strata. When the divider plate is properly adjusted as shown in Figure 2, the bed of particles moving in the launder will be split by the plate. Generally, coal particles 32 will pass over the plate, and refuse particles 33 will pass under the plate. When the horizontal distance from the leading edge 30 of plate 29 to outlet 18 is properly adjusted, the particles will arrange themselves generally as shown in Figure 2. In launders ranging from 7 to 14 inches in width, a horizontal distance from the outlet to the leading edge of the divider plate of 1 /2 to 2 inches has given satisfactory results. The upper strata of the bed will move across the upper surface of the plate. The area beneath the plate will, however, be relatively clear. Particles in the lower strata are torn from the bed adjacent edge 30 and carried into the passage beneath the plate at high speed. Some of the particles will pass through outlet 18, and others will continue downstream as indicated at 32 resuming formation of a bed downstream from plate 29. It is thought that the upwardly rising current from the box into the restricted passage beneath plate 29 causes a higher liquid velocity in this zone creating a resultant pressure drop beneath the plate, but the exact reason is uncertain.

The importance of the invention described herein may be best shown by reference to conditions observed on a modern Rheolaveur launder before and after the installation of apparatus embodying the invention. In a presently operating coal preparation plant, the fine coal was handled by passing it through two Rheolaveur free discharge launder systems of conventional, modern design. Both launder systems were required to handle the full feed to the plant, and were overloaded. The desired end product was metallurgical coal, and the plant was designed to further concentrate part of the launder product by tabling. It was necessary to employ a table operator to supervise operation of the tables. After installation of the invention in the launder systems and the removal of all barrages, those launders were able to handle the entire plant feed with no evidence of overloading; and they could handle a substantial increase in feed without overloading. The accuracy of separation so closely approaches the theoretical separation that the concentrating tables have been completely by-passed and are no longer used.

The following table shows the effects of the invention on the analysis of the products of the Rheolaveur launders. The raw coal feed contained approximately 16.2% ash and 2.51% sulfur. In Table I the particles were to be separated at a specific gravity of 1.60.

Table I Sink Clean Yield Float Material Clean Coal, Refuse, of Material in Clean Coal, Percent Percent Clean in Refuse, Coal, Percent S Ash Ash Coal, Percent Percent Percent 1. Theoretical Sink and Float tests. 0.0 1.68 7.0 73.2 87. 4 0.0 2. Conventional Lnunders Only. 1. 5 1. 71 7. 7 40. 9 74. 5 36. 0 3. Conventional Launders and Tabl 1.2 1.72 7. 8 53. 1 81.5 15.0 4. Launders Only with Divider Plates on all Boxes Going to Final Refuse, No Barrages- 1.0 1. 66 7.7 73.1 87.2 1.0

of the bed will be substantially less than in convnetional It will be noted that the yield of clean coal in'Example launders. Heavier particles will be withdrawn through the boxes in A, B, and C launders, although in view of the thin bed and its speed of movement, the operating characteristics for any given feed may be diflierent. As the bed in D and E launders approaches boxes 9 over which the divider plates have been installed, the particles will generally be Stratified according to their specific gravities. Coal particles 32, which are illustrated as dark particles, will generally be on top of the heavier particles of slate or refuse 33, which are shown with light centers. desired separating gravity of these tests was 1.50.

Table II we, i 5, Per- Pereent Percent cent 1. First Box -Oonventional Arrangement:

55.5 6.88 1.57 34.5 57.86 10. 49 Composite i 100. 23. 51 4. 65

2. First B0xD1vider Plate, No Barragez 1.50 Float 6. 7 8. 68 1.87 1.50 Sink 93. 3 74. 88 7. 13

Composite 100. 0 70. 08 6. 75

3. Second Box-Conventional Arrangement:

1.50 Float..- 87. 6. 48 1. 55 1.50 Sink"- 12.5 61.68 10.07

Composite"; 100. 0 12. 84 2. 70

4. Second BoxDivider Plate, No

Barrage:

I 1.50 Float 12.1 8.28 1. 77 1.50 Sink 87.9 73.80 I 8. 57

Composite 100.0 65. 50 7.82

The extraordinary increase in the withdrawal of sink material can readily be seen by comparison of the several examples.

. In making the above tests some boxes were closed off to permit proper bed formation, and the samples were taken from the first two open boxes on A launder. Referring to Figure 1, there were the second and fifth boxes on A launder, the first, third and fourth being closed 011. The launder was operated in the normal fashion and samples 1 and 3 were taken. Then-divider plates were installed over the open boxes, all barrages in the head end of A launder were removed, vertical water was supplied to the boxes and the launder was operated under similar load to take samples-2 and 1. It is to be noted that the invention permitted the withdrawal of an acceptable refuse, even at the head end of -A launder.

By use of the above described invention it has been possible to greatly increase the capacity of launder washers while substantially improving their product. It

has likewise been possible to eliminate the need forconcentrating tables, and the operation of the launders has become less critical. The capital expense required for new installations has been reduced, and a smaller crew of men has been able to handle a greater tonnage with less critical attention to operating conditions. The amount of circulating water is reduced by the practice of this invention, and it has substantially contributed to the maintenance of a closed water system in which no water is dumped to avoid a build-up of solids in the circulating water. The expense of avoiding stream pollution is thus substantially lessened. 1

While we have illustrated and described a present preferred embodiment of our invention, it is to be distinctly understood that we do not limit ourselves thereto and that our invention may be otherwise variously-practiced within the scope of the following claims.

We claim:

I. In a launder washer for hydraulic classification of solid particles in a fluid bed, a trough, at least one opening in the lower portion of said trough for the withdrawal of stratified particles from the trough, the trough being characterized by lack of any obstruction therein to free flow of the bed adjacent said opening, enclosure means below said opening for reception of particles discharged through said opening, means to supply fluid to the enclosure means, outlet means from said enclosure means, flow dividing means positioned in the trough above said opening therein and extending substantially the full width of the trough, said means being thin and flat to present low resistance to and low turbulence in a moving stream of particles in the trough and having the flat surface parallel to the surface of the bed dividing thestream whereby some of said particles pass above the thin flat means and other of said particles pass below said means. 2. In a launder washer for hydraulic classification of solid particles in a fluid bed, a trough along which a stream of said particles is moved, at least one opening in the lower portion of said trough for the withdrawal of stratified particles, the trough being characterized by lack of any obstruction therein to free flow of the bed adjacent said opening, enclosure means below said opening for reception of particles discharged through said opening, outlet means from said enclosure means, means to supply fluid within said enclosure means, a complanate bafile positioned above the opening with its large surface parallel to the surface of the bed for minimum turbulence and flow resistance to the stream of 'moving particles, said baffle dividing the stream of particles, some of said particles passing above the baflie and other of said particles passing below thebaffle. I

3. In a launder washer for hydraulic classification ofsolid particles having different specific gravities moving in a hydraulic stream, a trough, an opening in the bottom of said trough for withdrawal of particles of relatively high specific gravity, the trough being characterized by lack of obstruction therein to free flow of the bed adjacent the opening, enclosure means below said opening to receive particles discharged therethrough, means to supply fluid to the enclosure means, outlet means from said enclosure means, thin flow dividing means positioned in 'the trough above said opening within the stream of said particles moving down the trough with its larger surfaces generally parallel to the surface of the stream, andpre senting low resistance to flow of particles along the trough and creating low turbulence in the stream.

4. In a launder washer for hydraulic classification of solid particles having different specific gravities, an inclined trough, liquid supply means at the upper'end of said trough, said liquid carrying a bed of said particles down the incline of the trough, a plurality of particle withdrawal openings in the bottom of said trough, flow dividing means of small cross section'positioned within the trough over at least one of the openings for minimum flow resistance to and minimum turbulence in the bed and forming a passage of uniform transverse cross section along the length of the dividing means, the trough being characterized by lack of any obstruction adjacent the opening, adjusting means whereby the elevation of the dividing means may hev varied, enclosure means below each opening having dividing means associated therewith to receive particles withdrawn through said opening, fluid supply means connected to the enclosure mean and outlet means from the enclosure means.

5. In a launder washer for hydraulic classification of solid particles having different specific gravities, an inclined unobstructed trough along which a bed of said parallel to the bottom of the trough, plate adjusting 7 means whereby said plate may be positioned to skim off an upper layer of said bed and carry it across the opening, enclosure means below said openings to receive particles passing therethrough, means to supply fluid to said enclosure means, and outlet means from said enclosure means.

6. In a launder washer for hydraulic classification of solid particles having different specific gravities, an inclined trough along which a bed of said particles is carried by a flowing liquid stream, a plurality of particle withdrawal openings in the bottom of said trough, the trough being characterized by absence of any obstruction adjacent said openings, thin flat flow dividing means positioned adjacent some of said openings, each of said means comprisingv a thin. fiat divider. positioned. in tlief bedabove theassociated opening with. a. flat surface of the divider generally parallel to the surface of. the. bed; for low. turbulence. and. flow resistance, some of said particles. passing above the divider andother of said particles passing, below the, divider enclosure means be.- neath. eachsaid associated opening to-receive particles passing therethrough,. means to. supply. fluid tor-the en.- closure means, and; outlet. means. from the enclosure. means.

7. In. a. launder washer fonjhydraulic. classification of particles. having, diiferentt specific gravities,, an inclined trough .along which a bed of. said. particles :is carrifedlby a. flowing liquidstream, a plurality. of.-particle.,outlets-.-in. the bottom of saidtrough,, bafllemeans. positioned over at least one of said: outlets..at1d.. forming. a. passage to. said outlet parallel toand along. the. bottom o'f said, trough, said passage being of'unitprm transverse, cross section along the length of the passage: for. low. flow resistance. to and: turbulenee in. tbellowing. stream, adjustable bat-fie support. means whereby saidbaflle means,- may be. raised or lowered to vary. the effective height of said passage,, enclosure. means below each outlet having associated bafile means to receive particles passing throughthe out let, means to supply fluid; to the. enclosure means, and outlet means from they enclosure. means,

8. A launder washer for classifying particles of different specific gravitiescomprising a troughshaped washingsection, an outlet from said trough, meansabove said outlet forming anarrow passage of.uniformtransverse cross section. throughout its length. between said. means, and. the bottom of said. trough, said trough. being characterized by a smooth, .un obstructed surface for the, free. movement of particlesv therein, enclosure means below the outlet to receive particles-passingthrough the outlet, means to supplyfluid to ,the enclosuremeans, and outlet. means. from the enclosure. means.

9. A launder washer for hydraulic classification. of particles of different specific. gravities. in. a fluid stream comprising a plurality oftroughs, a plurality of particle outlets from said troughs, heavy particle. collecting.

means, complanate. flow dividing balfie. means adjacent each outletin, flow communication with said. heavy par.- ticle, collecting means, said baifie means being. parallel. to the surface of the stream. and. forming a low unobstructed. passage parallel. to, the bottom of. its. associatedtroughrfrom. whichpassage the associated outle.t div.erges,, enclosure means.b elow each said outlet. tov receive particles discharged through said associated outlets, fiuid supply means connectedto ,saidenclosure means, and out let means fromsaid. enclosure means.

10. A launder washer for hydraulic. classification of particles of difierent specificgravities comprisinga plurality of troughs, a plurality of. particle outlets from said troughs, refuse collecting, means, flow. dividing means adjacent each. outlet in flow. communication. with said collecting means, said. dividing, means. comprising a. thinflat. plate positioned parallel to the bottom of the associated. trough, the trough. being characterized. by lack of any obstruction adjacent said plate, said trough and plate presenting l'ow flow resistance to and low turbulence in a stream moving: in the trough, means vertically adjustably connecting the'plate and the trough, enclosure means beneath each said outlet in flow communication. with said collecting means to receive particles from said outlets, fluidsupply. meansconnected to said enclosure means, and outlet means from said enclosure means.

111. A launder-washer for classifying particles having different specific gravities comprising an unobstructed.- trough, an. opening, in the bottom of said trough for withdrawal of particles of relatively highspecific gravity, said' opening. discharging into enclosure means having another opening'therefrom, means to supply liquid to said enclosure means, outlet means from said enclosure means, and thin substantially smooth flow dividing means positionedinthe trough. within a stream of particles moving in the troughand having its plane parallel tothe surface causing minimum flow resistance and turbulence-in. the, moving stream.

12. A launder washer for classifying particles having different specific gravities comprising a smooth unobstructed trough, an outlet from said trough for withdrawal of particles of high density, means substantially enclosing the space beneath said outlet, outlet means from-the-enclosing means, means to supplyliquid tosaid enclosed space whereby an upward current of liquid maybe produced insaid outlet, and a complanate bafile adjustably positioned in'thetrough above the outlet forming a thin unobstructed passage of uniform transverse crosssection along its length above the bottom wall of the trough.

1-3; A launder'washer for hydraulic classification of particles of" difierent specific gravities comprising a: plu rality'ofsmooth-unobstrncted troughs, a plurality ofparticle' outlets from said troughs, heavy particle collecting means, substantiall'y flat particle bed dividing means adjustably' positioned in the trough adjacent each outlet in flow communication with said heavy particle collecting means, said dividing means being substantially parallel to the surface of a bed of particles in the trough, said dividing means forming a smooth flat passage along thebottom of the trough above each said outlet and developing minimum flow resistance to and minimum turbulence in amoving bed of the particles, space enclosing means. below each said outlet, particle escape means from said space enclosing means, and means supplying fluid to said space enclosing means whereby a rising current of fluid is maintained in the associated outlets.

References Cited in the file of this patent UNITED! STATES PATENTS Re;21,682 Stump Dec. 31, 1940 540,659 Hancock June 11, 1895' FOREIGN PATENTS 414,067 Germany" May 23, 1925 884,599 France July 31, 1942' 

